This invention relates to a condensing furnace, and, more particularly, to a compact, high efficiency condensing furnace.
The increasing demand for energy efficient furnaces has caused a reevaluation of condensing furnaces. Condensing furnaces have been known for many years, but they have never enjoyed widespread acceptance. For example, U.S. Pat. Nos. 1,990,827 and 2,290,255 disclose furnaces in which hot combustion gases flow from a combustion chamber through a series of heat exchangers. In each of these furnaces the temperature of the combustion gases is progressively lowered in each heat exchanger, and condensation of combustion products may occur in one or more of the heat exchangers.
Condensation of combustion products releases the latent heat of vaporization, thereby providing additional heat to the room air which is circulated past the heat exchangers. However, the condensate is very corrosive and can cause problems if not properly handled.
Perhaps another reason why the old condensing furnaces never achieved widespread use was the bulkiness of such furnaces. The furnaces illustrated in said prior patents are large, bulky, and heavy.
A more recent type of condensing furnace is described in U.S. Pat. No. 4,261,326. Three clamshell heat exchangers are used. Gas burners are positioned within two of the heat exchangers, and the hot combustion gases are directed to the third heat exchanger, where some condensation of combustion products may occur.